Add TagHandler#copy

Signed-off-by: TheMode <themode@outlook.fr>

src/main/java/net/minestom/server/tag/TagHandler.java

@@ -12,6 +12,8 @@ public interface TagHandler extends TagReadable, TagWritable {
 
     @NotNull TagReadable readableCopy();
 
+    @NotNull TagHandler copy();
+
     void updateContent(@NotNull NBTCompoundLike compound);
 
     @NotNull NBTCompound asCompound();

src/main/java/net/minestom/server/tag/TagHandlerImpl.java

@@ -13,9 +13,18 @@ import java.util.Arrays;
 import java.util.function.UnaryOperator;
 
 final class TagHandlerImpl implements TagHandler {
-    private volatile Entry<?>[] entries = new Entry[0];
+    private volatile Entry<?>[] entries;
     private Cache cache;
 
+    TagHandlerImpl(Entry<?>[] entries, Cache cache) {
+        this.entries = entries;
+        this.cache = cache;
+    }
+
+    TagHandlerImpl() {
+        this(new Entry[0], null);
+    }
+
     static TagHandlerImpl fromCompound(NBTCompoundLike compound) {
         TagHandlerImpl handler = new TagHandlerImpl();
         for (var entry : compound) {
@@ -60,6 +69,11 @@ final class TagHandlerImpl implements TagHandler {
         return updatedCache();
     }
 
+    @Override
+    public synchronized @NotNull TagHandler copy() {
+        return new TagHandlerImpl(entries.clone(), cache);
+    }
+
     @Override
     public void updateContent(@NotNull NBTCompoundLike compound) {
         final TagHandlerImpl converted = fromCompound(compound);

src/test/java/net/minestom/server/tag/TagHandlerCopyTest.java

@@ -0,0 +1,17 @@
+package net.minestom.server.tag;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class TagHandlerCopyTest {
+
+    @Test
+    public void copy() {
+        var handler1 = TagHandler.newHandler();
+        handler1.setTag(Tag.String("key"), "test");
+
+        var handler2 = handler1.copy();
+        assertEquals(handler1.getTag(Tag.String("key")), handler2.getTag(Tag.String("key")));
+    }
+}